Abstract:

In this study, Lactobacillus plantarum YW11 and SKT109 were separately incubated with skim milk. The crude
exopolysaccharides (EPSs) produced by the 2 strains were prepared by adding the culture with trichloroacetic acid to remove
proteins, followed by centrifugation, ethanol precipitation, dialysis and lyophilization, and they were further purified by
successive DEAE-Sepharose Fast Flow ion-exchange chromatography and Sepharose CL-6B gel filtration chromatography.
The monosaccharide composition of EPSs was analyzed by gas chromatography and their FT-IR spectra as well as
hydrodynamic radii (Rh) were determined using a KBr disc technique and dynamic light scattering, respectively. The results
showed that the EPS from strain YW11 was composed of glucose and galactose in a molar ratio of 3.45:1, and its Rh value
was calculated as approximately 69.20 nm. On the other hand, the EPS from strain SKT109 was composed of glucose and
galactose in a molar ratio of 1.43:1, and its Rh value was calculated as approximately 41.74 nm. The emulsifying capacity of
the EPS from YW11 strain was higher, but its emulsifying stability was lower than that of the EPS from SKT109. Both EPSs
had certain synergic emulsifying effects when either was mixed with other emulsifiers, with particle size of the emulsion
particles being mainly in the range of 1–2 μm. The EPSs produced by L. plantarum in this study have potentially promising
applications in food processing.

Key words: Lactobacillus plantarum, exopolysaccharides, isolation, purification, emulsifying properties